World No 2 Nadal's uncle and coach, Toni Nadal, has said that the 21-year-old is forced to take "a lot of precautions" before he competes and that they are trying to cut back on the number of matches he can play as a result of the injury.

"He's been affected by an injury to his foot since 2005. He has to learn how to live with it and so far he has managed for two years," Toni Nadal said.

"It's very serious. I don't know if it's career-threatening. I'll let the doctor reply to that. He has to take a lot of precautions when he plays."

Nadal, who won the third French Open title of his short career this season, depends much on his athletic ability, mobility and pace around the back of the court, but his style may have to be modified if he is to remain at the top of his game.

"We are pleased with the season just finished, with the injury and everything. His play has improved and the matches have been less intense," he said.

"Roger Federer is a fully-rounded player; Rafael has a different style. The key factor has been to shorten the length of matches and we have achieved that.

"His problem is that he has to play to maintain his physical tone and fitness levels. There's no other way to do it than by competing."

Nadal won six major tournaments in 2007 and reached the semi-finals of the end-of-season Masters Cup tournament in Shanghai where he was beaten by World No 1 Federer.